This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application APPARATUS FOR ADJUSTING HEAD-GAP OF INK-JET PRINTER filed with the Korean Industrial Property Office on Jan. 20, 2001 and there duly assigned Serial No. 3369/2001.
1. Field of the Invention
The present invention relates to an apparatus for adjusting a head gap of an ink jet printer, and, more particularly, to an apparatus for adjusting the head gap of the ink jet printer capable of automatically adjusting the head gap.
2. Description of the Related Art
Generally, an ink jet printer includes an eccentric shaft disposed in a main frame, a print head conveying bracket that is moved along the eccentric shaft, an ink cartridge disposed on the conveying bracket and having a print head, a conveying means for reciprocating the conveying bracket in a lengthwise direction of the eccentric shaft, and a head gap adjusting device for adjusting a head gap defined between the print head and a printing medium.
Based on image data input to the print head, the print head supplies ink to the printing medium and thereby forms an image on the printing medium. The conveying means includes a conveying belt disposed on the main frame for circulating in the lengthwise direction of the eccentric shaft, and includes a motor for circulating the conveying belt. The conveying belt is connected to the conveying bracket. Accordingly, the conveying bracket is moved together with the conveying belt that is circulated by the driving force of the motor.
The head gap adjusting device adjusts the head gap according to the thickness of the printing medium being supplied to the ink jet printer. The head gap adjusting device includes a bushing member rotatably disposed on the main frame, and a lever for turning the bushing member. The eccentric shaft is turned together with the bushing member. Accordingly, the height of the eccentric shaft is varied according to the position of the lever and, thus, the head gap is adjusted. For example, when the printing medium being supplied is a relatively thick material, such as an envelope, a user adjusts the head gap by turning the lever in a direction which will raise the eccentric shaft. When the printing medium being supplied is a relatively thinner material, such as an A4 sheet, the user adjusts the head gap by turning the lever in a direction which will lower the eccentric shaft.
According to the conventional apparatus for adjusting the head gap as described above there is, however, an inconvenience in that the user has to manually adjust the head gap. That is, the user has to manually turn the lever typically according to guesswork about the material and thickness of the printing medium.
Further, according to the above-described structure of an ink jet printer, the head gap typically cannot be variably adjusted. That is, the head gap adjusting device or apparatus is typically constructed to accommodate a limited type of printing medium, such as A4 sheet and envelope, or the like. Accordingly, the conventional head gap adjusting device apparatus typically cannot adjust the head gap efficiently according to printing mediums of different thickness.
The present invention has been made to overcome the above-mentioned problem of the related art, and accordingly, it is an object, among other objects, of the present invention to provide an apparatus for adjusting a head gap of an inkjet printer having an improved structure for automatically adjusting the head gap according to various types of the printing medium being supplied to the ink jet printer.
The above object, among other objects, of the present invention is accomplished by an apparatus for adjusting a head gap of an inkjet printer according to a first aspect of the present invention, the apparatus including: a main frame; an eccentric shaft including an eccentric supporting shaft at each end of the eccentric shaft, the eccentric shaft being rotatably disposed on the main frame by each eccentric supporting shaft; a head assembly movably disposed on the eccentric shaft, the head assembly including a print head for supplying an ink onto a printing medium for printing; a head gap detecting sensor for detecting the head gap defined between the printing medium and the print head; an eccentric shaft turning means for automatically adjusting the head gap by turning the eccentric shaft to move the eccentric shaft through a predetermined angle to move the head assembly to provide a predetermined head gap; and a controller for controlling the driving of the eccentric shaft turning means so as to move the eccentric shaft through the predetermined angle to compensate for the head gap detected by the head gap detecting sensor to provide the predetermined head gap.
The eccentric shaft turning means includes: a gear disposed on the eccentric supporting shaft; and a motor connected to the gear, the motor being driven under the control of the controller for rotating the gear in a predetermined direction by a predetermined angle.
The above object, among other objects, of the present invention is also accomplished by an apparatus for adjusting a head gap of an inkjet printer according to another or a second aspect of the present invention, the apparatus including: a main frame; a head assembly including a print head; an eccentric shaft for movably supporting the head assembly, the eccentric shaft including a supporting shaft at each end of the eccentric shaft, each supporting shaft being rotatably supported on the main frame; a turning means for adjusting the head gap between the print head and the printing medium by selectively turning the eccentric shaft forward in a first direction and backward in a second direction opposite to the first direction by a predetermined angle. The turning means includes a pivot lever or pivot member formed or displayed on the supporting shaft for pivotal movement together with a rotatable movement of the supporting shaft; a movable member movably disposed on or with respect to the main frame for reciprocating movement on or with respect to the main frame, the movable member for providing the pivotal movement or the pivot lever by a reciprocating movement of the movable member; a driving portion or driving means for providing the reciprocating movement of the movable member; and a controller for controlling the driving of the driving means or driving portion.
The movable member and the pivot lever each include a slant surface of a predetermined sloping degree, respectively, with the slant surface of the movable member being disposed in facing, opposing relation to the slant surface of the pivot member, and with the slant surface of the movable member and the slant surface of the pivot member each respectively moving in opposite directions during pivotal movement of the pivot member.
The slant surface of the movable member and the slant surface of the pivot member each includes a projection formed on the respective slant surface, for limiting a range of movement of the movable member and the pivot member and for preventing the movable member from being separated from contact with the pivot member.
The driving portion or driving means includes: a rack gear formed on a side of the movable member; a pinion gear rotatably formed on the main frame and for meshed engagement with the rack gear; and a motor for driving the pinion gear to provide the reciprocating movement of the movable member.
The eccentric shaft includes: a shaft body on which the head assembly is movably disposed; and bushing members on which both ends of the shaft body are eccentrically supported, with the bushing members being rotatably disposed on the main frame, the pivot lever or pivot member being incorporated with at least one bushing member.
Further, in the second aspect of an apparatus according to the present invention, there is provided a head gap detecting sensor disposed on the head assembly for detecting data corresponding to the head gap between a printing medium and the print head, and providing the detected data to the controller so that the controller can control the driving of the driving portion or driving means based on the detected data.
Further, in the second aspect of an apparatus according to the present invention, there is also provided a spring or spring member for elastically biasing the pivot lever or pivot member so as to a contact or position the pivot member in an engaging relation with the movable member.